Process for the direct oxidation of olefins to olefin oxides

ABSTRACT

A process and catalyst for the direct oxidation of an olefin having three or more carbon atoms, such as propylene, by oxygen to the corresponding olefin oxide, such as propylene oxide. The process involves contacting the olefin with oxygen under reaction conditions in the presence of hydrogen and in the presence of a catalyst. The catalyst comprises gold on a titanosilicate, preferably a microporous or mesoporous titanosilicate, such as, TS-1, TS-2, Ti-beta, Ti-ZSM-48, or Ti-MCM-41. Selectivity to the olefin oxide is high at good conversions of the olefin. The catalyst is readily regenerated, and the time between catalyst regenerations is long.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.09/458,559, filed Dec. 9, 1999, issued as U.S. Pat. No. 6,309,998, whichis a divisional of U.S. application Ser. No. 09/209,700, filed Dec. 11,1998, issued as U.S. Pat. No. 6,031,116, which is a continuation ofInternational Patent Application No. PCT/US97/11414, filed Jun. 30,1997, which was a continuation-in-part of U.S. application Ser. No.08/679,605, filed Jul. 11, 1996, now abandoned. This application alsoclaims the benefit of U.S. Provisional Application No. 60/021,013, filedJul. 1, 1996, U.S. Provisional Application No. 60/026,590, filed Sep.20, 1996, and U.S. Provisional Application No. 60/026,591, filed Sep.20, 1996.

BACKGROUND OF THE INVENTION

This invention pertains to a process and catalyst for the directoxidation of olefins, such as propylene, by oxygen to olefin oxides,such as propylene oxide.

Olefin oxides, such as propylene oxide, are used to alkoxylate alcoholsto form polyether polyols, such as polypropylene polyether polyols,which find significant utility in the manufacture of polyurethanes andsynthetic elastomers. Olefin oxides are also important intermediates inthe manufacture of alkylene glycols, such as propylene glycol anddipropylene glycol, and alkanolamines, such as isopropanolamine, whichare useful as solvents and surfactants.

Propylene oxide is produced commercially via the well-known chlorohydrinprocess wherein propylene is reacted with an aqueous solution ofchlorine to produce a mixture of propylene chlorohydrins. Thechlorohydrins are dehydrochlorinated with an excess of alkali to producepropylene oxide. This process suffers from the production of a lowconcentration salt stream. (See K. Weissermel and H. J. Arpe, IndustrialOrganic Chemistry, 2^(nd) ed., VCH Publishers, Inc., New York, N.Y.,1993, p. 264-265.)

Another well-known route to olefin oxides relies on the transfer of anoxygen atom from an organic hydroperoxide or peroxycarboxylic acid to anolefin. In the first step of this oxidation route, a peroxide generator,such as isobutane or acetaldehyde, is autoxidized with oxygen to form aperoxy compound, such as t-butyl hydroperoxide or peracetic acid. Thiscompound is used to epoxidize the olefin, typically in the presence of atransition metal catalyst, including titanium, vanadium, molybdenum, andother heavy metal compounds or complexes. Along with the olefin oxideproduced, this process disadvantageously produces equimolar amounts of acoproduct, for example an alcohol, such as t-butanol, or an acid, suchas acetic acid, whose value must be captured in the market place. (SeeIndustrial Organic Chemistry, ibid., p. 265-269.)

Although the direct oxidation of ethylene by molecular oxygen toethylene oxide has been commercialized with a silver catalyst, it isknown that the analogous direct oxidation of propylene exhibits a lowselectivity to the olefin oxide. Disadvantageously large amounts ofacrolein and oxygen-containing C₁₋₃ byproducts are produced, as taughtin Industrial Organic Chemistry, ibid., p. 264. Some patents representedby U.S. Pat. Nos. 4,007,135 and 4,845,253, teach the use ofmetal-promoted silver catalysts for the oxidation of propylene withoxygen to propylene oxide. Among the metal promoters disclosed are gold,beryllium, magnesium, calcium, barium, strontium, and the rare earthlanthanides. These promoted silver catalysts also exhibit lowselectivities to the olefin oxide.

Alternatively, EP-A1-0,709,360 discloses a process of oxidizing anunsaturated hydrocarbon, such as propylene, with oxygen in the presenceof hydrogen and a catalyst to form an epoxide, such as propylene oxide.Gold deposited on titanium dioxide, further immobilized on a carriersuch as silica or alumina, is taught as the catalyst composition. Thecatalyst exhibits lower olefin oxide selectivity and less efficienthydrogen consumption when operated at higher temperatures. Additionally,the catalyst has a short run time.

PCT publication WO-A1-96/02323 discloses the oxidation of an olefin,including propylene, with oxygen in the presence of hydrogen and acatalyst to form an olefin oxide. The catalyst is a titanium or vanadiumsilicalite containing at least one platinum group metal, and optionally,an additional metal selected from gold, iron, cobalt, nickel, rhenium,and silver. The productivity of olefin oxide is low in this process.

In view of the above, a need continues to exist in the chemical industryfor an efficient direct route to propylene oxide and higher olefinoxides from the reaction of oxygen with C₃ and higher olefins. Thediscovery of such a process which simultaneously achieves highselectivity to the olefin oxide at an economically advantageousconversion of the olefin would represent a significant achievement overthe prior art. For commercial viability such a process would alsorequire that the catalyst exhibit a long lifetime.

U.S. Pat. Nos. 4,839,327 and 4,937,219 represent additional artdisclosing a composition comprising gold particles having a particlesize smaller than about 500 Å immobilized on an alkaline earth oxide ortitanium dioxide or a composite oxide of titanium dioxide with analkaline earth oxide. A preparation of this composition involvesdeposition of a gold compound onto the alkaline earth oxide, titaniumdioxide, or the composite oxide, followed by calcination so as toproduce metallic gold of a particle size smaller than about 500 Å. Thisteaching is silent with respect to depositing the gold particles on atitanosilicate and to a process for producing olefin oxides.

SUMMARY OF THE INVENTION

This invention is a novel process of preparing an olefin oxide directlyfrom an olefin and oxygen. The process comprises contacting an olefinhaving at lcast three carbon atoms with oxygen in the presence ofhydrogen and in the presence of a catalyst under process conditionssufficient to produce the corresponding olefin oxide. The uniquecatalyst which is employed in the process of this invention comprisesgold on a titanosilicate.

The novel process of this invention is useful for producing an olefinoxide directly from oxygen and an olefin having three or more carbonatoms. Unexpectedly, the process of this invention produces the olefinoxide in a remarkably high selectivity. Partial and complete combustionproducts, such as acrolein and carbon dioxide, which are found in largeamounts in many prior art processes, are produced in lesser amounts inthe process of this invention. Significantly, the process of thisinvention can be operated at a high temperature, specifically greaterthan about 120° C., while maintaining a high selectivity to olefinoxide. Operation at higher temperatures advantageously provides steamcredits from the heat produced. Accordingly, the process of thisinvention can be integrated into a total plant design wherein the heatderived from the steam is used to drive additional processes, forexample, the separation of the olefin oxide from water. Even moreadvantageously, since water is produced as a byproduct of this process,the hydrogen efficiency, as measured by the water to olefin oxide molarratio, is good. Most advantageously, the process in its preferredembodiments exhibits an olefin conversion which is good.

In another aspect, this invention is a unique catalyst compositioncomprising gold on a titanosilicate.

The novel composition of this invention can be effectively used in theaforementioned direct oxidation of an olefin having three or more carbonatoms to the corresponding olefin oxide. Besides being active and highlyselective for the olefin oxide, the catalyst exhibits evidence of a longlifetime. As a further advantage, when partially or completely spent,the catalyst is easy to regenerate. Accordingly, this unique catalystexhibits highly desirable properties for the process of oxidizingpropylene and higher olefins to their corresponding olefin oxides.

DETAILED DESCRIPTION OF THE INVENTION

The novel process of this invention comprises contacting an olefinhaving at least three carbon atoms with oxygen in the presence ofhydrogen and an epoxidation catalyst under process conditions sufficientto prepare the corresponding olefin oxide. In one preferred embodiment,a diluent is employed with one or more of the reactants, as described indetail hereinafter. The relative molar quantities of olefin, oxygen,hydrogen, and optional diluent can be any which are sufficient toprepare the desired olefin oxide. In a preferred embodiment of thisinvention, the olefin employed is a C₃₋₁₂ olefin, and it is converted tothe corresponding C₃₋₁₂ olefin oxide. In a more preferred embodiment,the olefin is a C₃₋₈ olefin, and it is converted to the correspondingC₃₋₈ olefin oxide. In a most preferred embodiment, the olefin ispropylene, and the olefin oxide is propylene oxide.

The novel catalyst which is employed in the epoxidation process of thisinvention comprises gold on a titanosilicate. The titanosilicate isgenerally characterized as having a framework structure formed from SiO₄⁴⁻ tetrahedra wherein a portion of the silicon atoms is replaced withtitanium atoms. Preferably, the titanosilicate is a poroustitanosilicate. In this preferred form, a series of pores or channels orcavities exists within the framework structure, thereby giving thetitanosilicate its porous properties. A most preferred form of thetitanosilicate is titanium silicalite-1 (TS-1) having a crystallinestructure, as determined by X-ray diffraction (XRD), which isisomorphous to the structure of zeolite ZSM-5 and the pure silica formof ZSM-5 known as “silicalite”. In a more preferred embodiment of thecatalyst, the gold exists in the form of clusters having an averageparticle size of about 10 Å or greater, as determined by transmissionelectron microscopy (TEM).

Any olefin containing three or more carbon atoms can be employed in theprocess of this invention. Monoolefins are preferred, but compoundscontaining two or more olefins, such as dienes, can also be employed.The olefin can be a simple hydrocarbon containing only carbon andhydrogen atoms. Alternatively, the olefin can be substituted at any ofthe carbon atoms with an inert substituent. The term “inert”, as usedherein, requires the substituent to be substantially non-reactive in theprocess of this invention. Suitable inert substituents include, but arenot limited to, halide, ether, ester, alcohol, and aromatic moieties,preferably, chloro, C₁₋₁₂ ether, ester, and alcohol moieties, and C₆₋₁₂aromatic moieties. Non-limiting examples of olefins which are suitablefor the process of this invention include propylene, 1-butene, 2-butene,2-methylpropene, 1-pentene, 2-pentene, 2-methyl-1-butene,2-methyl-2-butene, 1-hexene, 2-hexene, 3-hexene, and analogously, thevarious isomers of methylpentene, ethylbutene, heptene, methylhexene,ethylpentene, propylbutene, the octenes, including preferably 1-octene,and other higher analogues of these; as well as butadiene,cyclopentadiene, dicyclopentadiene, styrene, a-methylstyrene,divinylbenzene, allyl chloride, allyl alcohol, allyl ether, allyl ethylether, allyl butyrate, allyl acetate, allyl benzene, allyl phenyl ether,ally propyl ether, and allyl anisole. Preferably, the olefin is anunsubstituted or substituted C₃₋₁₂ olefin, more preferably, anunsubstituted or substituted C₃₋₈ olefin. Most preferably, the olefin ispropylene. Many of the aforementioned olefins are availablecommercially; others can be prepared by chemical processes known tothose skilled in the art.

The quantity of olefin employed in the process can vary over a widerange provided that the corresponding olefin oxide is produced.Generally, the quantity of olefin employed depends upon the specificprocess features, including for example, the design of the reactor, thespecific olefin, and economic and safety considerations. Those skilledin the art can determine a suitable range of olefin concentrations forthe specific process features desired. Generally, on a molar basis anexcess of olefin is used relative to the oxygen, because this conditionenhances the productivity to olefin oxide. Based on the processconditions disclosed herein, typically, the quantity of olefin isgreater than about 1, preferably, greater than about 10, and morepreferably, greater than about 20 mole percent, based on the total molesof olefin, oxygen, hydrogen, and optional diluent. Typically, thequantity of olefin is less than about 99, preferably, less than about85, and more preferably, less than about 70 mole percent, based on thetotal moles of olefin, oxygen, hydrogen, and optional diluent.

Oxygen is also required for the process of this invention. Any source ofoxygen is acceptable, including air and essentially pure molecularoxygen. Other sources of oxygen may be suitable, including ozone, andnitrogen oxides, such as nitrous oxide. Molecular oxygen is preferred.The quantity of oxygen employed can vary over a wide range provided thatthe quantity is sufficient for producing the desired olefin oxide.Ordinarily, the number of moles of oxygen per mole of olefin used in thefeedstream is less than 1. Under these conditions the conversion ofolefin and selectivity to olefin oxide are enhanced while theselectivity to combustion products, such as carbon dioxide, isminimized. Preferably, the quantity of oxygen is greater than about0.01, more preferably, greater than about 1, and most preferably greaterthan about 5 mole percent, based on the total moles of olefin, hydrogen,oxygen, and optional diluent. Preferably, the quantity of oxygen is lessthan about 30, more preferably, less than about 25, and most preferablyless than about 20 mole percent, based on the total moles of olefin,hydrogen, oxygen, and optional diluent. Above about 20 mole percent, theconcentration of oxygen may fall within the flammable range forolefin-hydrogen-oxygen mixtures.

Hydrogen is also required for the process of this invention. In theabsence of hydrogen, the activity of the catalyst is significantlydecreased. Any source of hydrogen can be used in the process of thisinvention, including for example, molecular hydrogen obtained from thedehydrogenation of hydrocarbons and alcohols. In an alternativeembodiment of this invention, the hydrogen may be generated in situ inthe olefin oxidation process, for example, by dehydrogenating alkanes,such as propane or isobutane, or alcohols, such as isobutanol.Alternatively, hydrogen may be used to generate a catalyst-hydridecomplex or a catalyst-hydrogen complex which can provide the necessaryhydrogen to the process.

Any quantity of hydrogen can be employed in the process provided thatthe amount is sufficient to produce the olefin oxide. Suitablequantities of hydrogen are typically greater than about 0.01,preferably, greater than about 0.1, and more preferably, greater thanabout 3 mole percent, based on the total moles of olefin, hydrogen,oxygen, and optional diluent. Suitable quantities of hydrogen aretypically less than about 50, preferably, less than about 30, and morepreferably, less than about 20 mole percent, based on the total moles ofolefin, hydrogen, oxygen, and optional diluent.

In addition to the above reagents, it may be desirable to employ adiluent with the reactants, although the use thereof is optional. Sincethe process of this invention is exothermic, a diluent beneficiallyprovides a means of removing and dissipating the heat produced. Inaddition the diluent provides an expanded concentration regime in whichthe reactants are non-flammable. The diluent can be any gas or liquidwhich does not inhibit the process of this invention. The specificdiluent chosen will depend upon the manner in which the process isconducted. For example, if the process is conducted in a gas phase, thensuitable gaseous diluents include, but are not limited to, helium,nitrogen, argon, methane, carbon dioxide, steam, and mixtures thereof.Most of these gases are essentially inert with respect to the process ofthis invention. Carbon dioxide and steam may not necessarily be inert,but may have a beneficial promoting effect. If the process is conductedin a liquid phase, then the diluent can be any oxidation stable andthermally stable liquid.

Examples of suitable liquid diluents include aliphatic alcohols,preferably C₁₋₁₀ aliphatic alcohols, such as methanol and t-butanol;chlorinated aliphatic alcohols, preferably C₁₋₁₀ chlorinated alkanols,such as chloropropanol; chlorinated aromatics, preferably chlorinatedbenzenes, such as chlorobenzene and dichlorobenzene; as well as liquidpolyethers, polyesters, and polyalcohols.

If used, the amount of diluent is typically greater than about 0,preferably greater than about 0.1, and more preferably, greater thanabout 15 mole percent, based on the total moles of olefin, oxygen,hydrogen, and diluent. The amount of diluent is typically less thanabout 90, preferably, less than about 80, and more preferably, less thanabout 70 mole percent, based on the total moles of olefin, oxygen,hydrogen, and diluent.

The aforementioned concentrations of olefin, oxygen, hydrogen, anddiluent are suitably based on the reactor designs and process parametersdisclosed herein. Those skilled in the art will recognize thatconcentrations other than the aforementioned ones may be suitablyemployed in other various engineering realizations of the process.

The unique catalyst which is beneficially employed in the process ofthis invention comprises gold on a titanosilicate. Surprisingly, gold incombination with a titanosilicate can exhibit catalytic oxidationactivity and enhanced selectivity for olefin oxides. Preferably, thecatalyst of this invention is essentially free of palladium. The term“essentially free” means that the concentration of palladium is lessthan about 0.01 weight percent, preferably, less than about 0.005 weightpercent, based on the total weight of the catalyst. More preferably, thecatalyst of this invention is essentially free of the Group VIII metals,which means that the total concentration of these metals is less thanabout 0.01 weight percent, preferably, less than about 0.005 weightpercent, based on the total weight of the catalyst. The Group VIIImetals include iron, cobalt, nickel, ruthenium, rhodium, palladium,osmium, iridium, and platinum.

The gold predominantly exists as elemental metallic gold, as determinedby X-ray photoelectron spectroscopy or X-ray absorption spectroscopy,although higher oxidation states may also be present. Most of the goldappears from TEM studies to be deposited on the surface of thetitanosilicate; however, the deposition of individual gold atoms orsmall gold clusters in the pores or on any extra-framework titania orthe inclusion of ionic gold into the silica framework may also occur.Preferably, the gold is not associated with any extra-framework titaniaor titania added as a support, as analyzed by TEM. Typically, theaverage gold particle size (or diameter) is about 10 Å or greater, asmeasured by TEM. Preferably, the average gold particle size is greaterthan about 10 Å, more preferably, greater than about 12 Å, and mostpreferably, greater than about 25 Å. Preferably, the average goldparticle size is less than about 500 Å, more preferably, less than about200 Å, and most preferably, less than about 100 Å.

The titanosilicate is characterized by a framework structure formed fromSiO₄ ⁴⁻ tetrahedra and nominally TiO₄ ⁴⁻ tetrahedra. The titanosilicatecan be crystalline, which implies that the framework has a periodicregularity which is identifiable by X-ray diffraction (XRD).Alternatively, the titanosilicate can be amorphous, which implies arandom or non-periodic framework which does not exhibit a well-definedXRD pattern.

Any titanosilicate can be employed in the catalyst of this invention.Preferably, the titanosilicate is porous, which means that within thetitanosilicate framework structure there exists a regular or irregularsystem of pores or channels. Empty cavities, referred to as “cages”, canalso be present. The pores can be isolated or interconnecting, and theycan be one, two, or three dimensional. Preferably, the pores aremicropores or mesopores or some combination thereof. For the purposes ofthis invention, a micropore has a pore diameter (or critical dimensionas in the case of a non-circular perpendicular cross-section) rangingfrom about 4 Å to about 20 Å, while a mesopore has a pore diameter orcritical dimension ranging from greater than about 20 Å to about 200 Å.The combined volume of the micropores and the mesopores preferablycomprises about 70 percent or greater of the total pore volume, andpreferably, about 80 percent or greater of the total pore volume. Thebalance of the pore volume comprises macropores which have a porediameter of greater than about 200 Å. These macropores will also includethe void spaces between particles or crystallites.

The pore diameter (or critical dimension), pore size distribution, andsurface area of the porous titanosilicate can be obtained from themeasurement of adsorption isotherms and pore volume. Typically, themeasurements are made on the titanosilicate in powder form using as anadsorbate nitrogen at 77 K or argon at 88 K and using any suitableadsorption analyzer, such as a Micromeritics ASAP 2000 instrument.Measurement of micropore volume is derived from the adsorption volume ofpores having a diameter in the range from about 4 Å to about 20 Å.Likewise, measurement of mesopore volume is derived from the adsorptionvolume of pores having a diameter in the range from greater than about20 Å to about 200 Å. From the shape of the adsorption isotherm, aqualitative identification of the type of porosity, for example,microporous or macroporous, can be made. Additionally, increasedporosity can be correlated with increased surface area. Pore diameter(or critical dimension) can be calculated from the data using equationsdescribed by Charles N. Satterfield in Heterogeneous Catalysis inPractice, McGraw-Hill Book Company, New York, 1980, pp. 106-114,incorporated herein by reference.

Additionally, crystalline titanosilicates can be identified by X-raydiffraction(XRD), either by comparing the XRD pattern of the material ofinterest with a previously published standard or by analyzing the XRDpattern of a single crystal to determine framework structure, and ifpores are present, the pore geometry and pore size.

Non-limiting examples of porous titanosilicates which are suitablyemployed in the process of this invention include porous amorphoustitanosilicates; porous layered titanosilicates; crystalline microporoustitanosilicates, such as titanium silicalite-1 (TS-1), titaniumsilicalite-2 (TS-2), titanosilicate beta (Ti-beta), titanosilicateZSM-12 (Ti-ZSM-12) and titanosilicate ZSM-48 (Ti-ZSM-48); and mesoporoustitanosilicates, such as Ti-MCM-41.

TS-1 possesses an MFI crystalline structure which is isomorphous to thecrystalline structure of zeolite ZSM-5 and isomorphous to the structureof the pure silica form of ZSM-5 known as “silicalite. Thethree-dimensional framework structure of the pure silica “silicalite” isformally constructed from tetrahedral SiO₄ ⁴⁻ units. In ZSM-5 some ofthe silica tetrahedra are replaced with AlO₄ ⁵⁻ tetrahedra, and acation, such as sodium ion, is needed to balance charge requirements. InTS-1 some of the silica tetrahedra are replaced with TiO₄ ⁴⁻ tetrahedra.In this replacement, the overall charge remains electronically neutraland no additional cations are required. The pore structure of TS-1comprises two interconnecting, roughly cylindrical, 10-ring pores ofabout 5 Å diameter. A 10-ring pore is formed from ten tetrahedral units.Titanium silicalite and its characteristic XRD pattern have beenreported in U.S. Pat. No. 4,410,501, incorporated herein by reference.TS-1 can be obtained commercially, but it can also be synthesizedfollowing the methods described in U.S. Pat. No. 4,410,501. Otherpreparations have been reported by the following (incorporated herein byreference): A. Tuel, Zeolites, 1996, 16, 108-117; by S. Gontier and A.Tuel, Zeolites, 1996, 16, 184-195; by A. Tuel and Y. Ben Taarit inZeolites, 1993, 13, 357-364; by A. Tuel, Y. Ben Taarit and C. Naccachein Zeolites, 1993, 13, 454-461; by A. Tuel and Y. Ben Taarit inZeolites, 1994, 14, 272-281; and by A. Tuel and Y. Ben Taarit inMicroporous Materials, 1993, 1, 179-189.

TS-2 possesses an MEL topology which is isomorphous to the topology ofthe aluminosilicate ZSM-11. The pore structure of TS-2 comprises onethree-dimensional, microporous, 10-ring system. TS-2 can be synthesizedby methods described in the following references (incorporated herein byreference): J. Sudhakar Reddy and R. Kumar, Zeolites, 1992, 12, 95-100;by J. Sudhakar Reddy and R. Kumar, Journal of Catalysis, 1991, 130,440-446; and by A. Tuel and Y. Ben Taarit, Applied Catal. A, General,1993, 102, 69-77.

Ti-beta possesses a BEA crystalline structure which is isomorphous tothe aluminosilicate beta. The pore structure of Ti-beta comprises twointerconnecting 12-ring, roughly cylindrical pores of about 7 Ådiameter. The structure and preparation of titanosilicate beta have beendescribed in the following references, incorporated herein by reference:PCT patent publication WO 94/02245 (1994); M. A. Camblor, A. Corma, andJ. H. Perez-Pariente, Zeolites, 1993, 13, 82-87; and M. S. Rigutto, R.de Ruiter, J. P. M. Niederer, and H. van Bekkum, Stud. Surf. Sci. Cat.,1994, 84, 2245-2251.

Ti-ZSM-12 possesses an MTW crystalline structure which is isomorphous tothe aluminosilicate ZSM-12. The pore structure of Ti-ZSM-12 comprisesone, one-dimensional 12-ring channel system of dimensions 5.6×7.7 Å, asreferenced by S. Gontier and A. Tuel, ibid., incorporated herein byreference.

Ti-ZSM-48 possesses a crystalline structure which is isomorphous to thealuminosilicate ZSM-48. The pore structure of Ti-ZSM-48 comprises aone-dimensional 10-ring channel system of dimensions 5.3 Å by 5.6 Å, asreferenced by R. Szostak, Handbook of Molecular Sieves, Chapman & Hall,New York, 1992, p. 551-553. Other references to the preparation andproperties of Ti-ZSM-48 include C. B. Dartt, C. B. Khouw, H. X. Li, andM. E. Davis, Microporous Materials, 1994, 2, 425-437; and A. Tuel and Y.Ben Taarit, Zeolites, 1996, 15, 164-170, the aforementioned referencesbeing incorporated herein by reference.

Ti-MCM-41 is a hexagonal phase isomorphous to the aluminosilicateMCM-41. The channels in MCM-41 are one-dimensional with diametersranging from about 28 Å to 100 Å. Ti-MCM-41 can be prepared as describedin the following citations, incorporated herein by reference: S. Gontierand A. Tuel, Zeolites, 1996, 15, 601-610; and M. D. Alba, Z. Luan, andJ. Klinowski, J. Phys. Chem., 1996, 100, 2178-2182.

The silicon to titanium atomic ratio (Si/Ti) of the titanosilicate canbe any ratio which provides for an active and selective epoxidationcatalyst in the process of this invention. A generally advantageousSi/Ti atomic ratio is equal to or greater than about 5/1, andpreferably, equal to or greater than about 10/1. A generallyadvantageous Si/Ti atomic ratio is equal to or less than about 200/1,preferably, equal to or less than about 100/1. The Si/Ti atomic ratiodefined hereinabove refers to a bulk ratio which includes the total ofthe framework titanium and the extra-framework titanium. At high Si/Tiratios, for example, about 100/1 or more, there may be littleextra-framework titanium and the bulk ratio essentially corresponds tothe framework ratio.

In one preferred embodiment of this invention, the catalyst issubstantially free of the anatase phase of titanium dioxide, morepreferably, substantially free of crystalline titanium dioxide, and mostpreferably, free of titanium dioxide. Crystalline titanium dioxide maybe present, for example, as extra-framework titania or titania added asa carrier or support. Raman spectroscopy can be used to determine thepresence of crystalline titanium dioxide. The anatase phase of titaniumdioxide exhibits a characteristic strong, sharp Raman peak at about 147cm⁻¹. The rutile phase exhibits Raman peaks at about 448 cm⁻¹ and about612 cm⁻¹. The brookite phase, which usually is available only as anatural mineral, exhibits a characteristic peak at about 155 cm⁻¹. Therutile and brookite peaks have a lower intensity than the 147 cm⁻¹ peakof anatase. In the aforementioned more preferred embodiment of thecatalyst, Raman peaks for the anatase, rutile, and brookite phases oftitanium dioxide are essentially absent. When the catalyst exhibitsessentially no detectable peaks at the aforementioned wavenumbers, thenit is estimated that less than about 0.02 weight percent of the catalystexists in the form of crystalline titanium dioxide. Raman spectra can beobtained on any suitable laser Raman spectrometer equipped, for example,with an argon ion laser tuned to the 514.5 nm line and having a laserpower of about 90 to 100 mW measured at the sample.

The loading of the gold on the titanosilicate can be any loading whichgives rise to the desired olefin oxide product. Generally, the goldloading is greater than about 0.01 weight percent, based on the totalweight of gold and titanosilicate. Generally, the loading is less thanabout 20 weight percent. Preferably, the gold loading is greater thanabout 0.03, more preferably, greater than about 0.05 weight percent.Preferably, the gold loading is less than about 10.0, more preferably,less than about 5.0 weight percent.

The gold component can be deposited or supported on the titanosilicateby any method known in the art which provides for an active andselective catalyst. Non-limiting examples of known deposition methodsinclude impregnation, ion-exchange, and deposition by precipitation. Apreferred deposition method is disclosed by S. Tsubota, M. Haruta, T.Kobayashi, A. Ueda, and Y. Nakahara, “Preparation of Highly DispersedGold on Titanium and Magnesium Oxide,” in Preparation of Catalysts V, G.Poncelet, P. A. Jacobs, P. Grange, and B. Delmon, eds., Elsevier SciencePublishers B. V., Amsterdam, 1991, p. 695ff, incorporated herein byreference. This method involves contacting the titanosilicate with anaqueous solution of a soluble gold compound at a temperature and pHsufficient to precipitate the gold compound onto the titanosilicate.Non-aqueous solutions can also be employed. Thereafter, in the preferredmethod of this invention which is different from the aforementionedreference, the gold/titanosilicate composite is not washed or is lightlywashed, with preferably no more than about 100 ml wash liquid per gramcomposite. Then, the composite is calcined or reduced at a temperaturesufficient to reduce the gold substantially to metallic gold having anaverage particle size between about 10 Å and about 500 Å.

For aqueous solvents, any water soluble gold compound can be used, suchas chloroauric acid, sodium chloroaurate, potassium chloroaurate, goldcyanide, potassium gold cyanide, and diethylamine auric acidtrichloride. Typically, the molarity of the soluble gold compound rangesfrom about 0.001 M to the saturation point of the soluble gold compound,preferably, from about 0.005 M to about 0.5 M. The desired quantity oftitanosilicate is added to the solution, or vice versa; and the pH isadjusted to between about 5 and about 11, preferably, between about 6and about 9, with any suitable base, such as a Group 1 hydroxide orcarbonate, preferably, sodium hydroxide, sodium carbonate, potassiumcarbonate, cesium hydroxide, and cesium carbonate. Thereafter, themixture is stirred under air at a temperature between about 20° C. andabout 80° C. for a time ranging from about 1 hour to about 15 hours. Atthe end of this period, the solids are recovered and optionally washedwith water, the water optionally containing promoter metal salts,described hereinbelow, preferably at a pH between about 5 and 11.Typically thereafter, the solids are dried under air at a temperaturebetween about 80° C. and about 110° C. The solid is then calcined underair, or calcined in a reducing atmosphere, such as hydrogen, or heatedin an inert atmosphere, such as nitrogen, at a temperature between about250° C. and about 800° C. for a time from about 1 hour to about 24 hoursto form a titanosilicate having metallic gold thereon.

Optionally, the catalyst of this invention can contain a promoter metalor a combination of promoter metals. Any metal ion having a valencebetween +1 and +7 which enhances the productivity of the catalyst in theoxidation process of this invention can be employed as a promoter metal.Factors contributing to increased productivity of the catalyst includeincreased conversion of the olefin, increased selectivity to the olefinoxide, decreased production of water, and increased catalyst lifetime.Non-limiting examples of suitable promoter metal include the metals ofGroups 1 through 12 of the Periodic Table of the Elements, as well asthe rare earth lanthanides and actinides, as referenced in the CRCHandbook of Chemistry and Physics, 75^(th) ed., CRC Press, 1994.Preferably, the promoter metal is selected from Group 1 metals of thePeriodic Table including lithium, sodium, potassium, rubidium, andcesium; from Group 2 metals, including beryllium, magnesium, calcium,strontium, and barium; from the lanthanide rare earth metals, includingcerium, praseodymium, neodymium, promethium, samarium, europium,gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium,and lutetium; and the actinide metals, specifically, thorium anduranium, or from a combination of these metals. More preferably, thepromoter metal is magnesium, calcium, barium, erbium, lutetium, lithium,potassium, rubidium, cesium, or a combination thereof. In anotherpreferred embodiment, the promoter metal excludes palladium, and evenmore preferably, excludes a Group VIII metal, including, iron, cobalt,nickel, ruthenium, rhodium, palladium, osmiurn, iridium, and platinum.As used herein the word “excludes” means that the concentration of themetal is less than about 0.01, preferably, less than about 0.005 weightpercent, based on the total weight of the catalyst.

If one or more promoter metals arc used as described hereinabove, thenthe total quantity of promoter metal(s) generally is greater than about0.01, preferably, greater than about 0.10, and more preferably, greaterthan about 0.15 weight percent, based on the total weight of thecatalyst. The total quantity of promoter metal(s) is generally less thanabout 20, preferably, less than about 15, and more preferably, less thanabout 10 weight percent, based on the total weight of the catalyst.

The promoter metal(s) can be deposited or supported onto thetitanosilicate simultaneously with the gold particles, or alternatively,in a separate step either before or after the gold is deposited orsupported. Generally, the promoter metal is deposited from an aqueous ororganic solution containing a soluble promoter metal salt. Any salt ofthe promoter metal which has adequate solubility can be used; forexample, the metal nitrates, carboxylates, and halides, preferably thenitrates, are suitable. If an organic solvent is employed, it can be anyof a variety of known organic solvents, including, for example,alcohols, esters, ketones, and aliphatic and aromatic hydrocarbons.Ordinarily, the titanosilicate is contacted with the solution of thepromoter metal salt under conditions which are similar to those used forcontacting the titanosilicate with the gold solution. After the promotermetal is deposited, washing is optional. If done to excess, washing canleach at least a portion of the promoter metal out of the catalyst.Afterwards, calcination under air or under a reducing atmosphere orheating in an inert gas is conducted in a manner similar to thatdescribed hereinabove for the gold deposition.

Optionally, the catalyst of this invention can be extruded with, boundto, or supported on a second support, such as silica, alumina, analuminosilicate, magnesia, titania, carbon, or mixtures thereof. Thesecond support may function to improve the physical properties of thecatalyst, such as, the strength or attrition resistance, or to bind thecatalyst particles together. Generally, the quantity of second supportranges from about 0 to about 95 weight percent, based on the combinedweight of the catalyst and second support. It is noted that although thecatalyst of this invention can be physically mixed or extruded withtitania or bound to titania as a second support, in a preferredembodiment the catalyst is substantially free of the anatase phase oftitanium dioxide, more preferably free of crystalline titanium dioxide,as noted hereinabove. If titania is used as a second support, however,note that its presence may interfere with the analytical identificationof the catalyst. In this instance especially, analysis of the catalystshould be made in the absence of the second support.

The process of this invention can be conducted in a reactor of anyconventional design suitable for gas or liquid phase processes. Thesedesigns broadly include batch, fixed-bed, transport bed, fluidized bed,moving bed, trickle bed, and shell and tube reactors, as well ascontinuous and intermittent flow and swing reactor designs.Alternatively, the process may be conducted in two-steps wherein thecatalyst is first contacted with oxygen and thereafter the oxygenatedcatalyst is contacted with a mixture of propylene and hydrogen.Preferably, the process is conducted in the gas phase and the reactor isdesigned with heat transfer features for the removal of the heatproduced. Preferred reactors designed for these purposes includefixed-bed, shell and tube, fluidized bed, and moving bed reactors, aswell as swing reactors constructed from a plurality of catalyst bedsconnected in parallel and used in an alternating fashion.

The process conditions for the direct oxidation described herein canvary considerably over a nonflammable and flammable regime. It isbeneficial, however, to recognize the conditions which distinguishbetween nonflammable and flammable mixtures of the olefin, hydrogen, andoxygen. Accordingly, a phase diagram can be constructed or consultedwhich for any given process temperature and pressure shows the flammableand non-flammable range of reactant compositions, including the diluent,if used. The more preferred reactant mixtures specified hereinabove arcbelieved to lie outside the flammable regime when the process isoperated at the more preferred temperatures and pressures specifiedhereinbelow. Nevertheless, operation within the flammable regime ispossible, as designed by one skilled in the art.

Usually, the process is conducted at a temperature which is greater thanabout ambient, taken as 20° C., preferably, greater than about 70° C.,more preferably greater than about 120° C. Usually, the process isconducted at a temperature less than about 250° C., preferably less thanabout 225° C., more preferably, less than about 200° C. Preferably, thepressure ranges from about atmospheric to about 400 psig (2758 kPa),more preferably, from about 150 psig (1034 kPa) to about 250 psig (1724kPa).

In flow reactors the residence time of the reactants and the molar ratioof reactants to catalyst will be determined by the space velocity. For agas phase process the gas hourly space velocity (GHSV) of the olefin canvary over a wide range, but typically is greater than about 10 ml olefinper ml catalyst per hour (hr⁻¹), preferably greater than about 100 hr⁻¹,and more preferably, greater than about 1,000 hr⁻¹. Typically, the GHSVof the olefin is less than about 50,000 hr⁻¹, preferably, less thanabout 35,000 hr⁻¹, and more preferably, less than about 20,000 hr⁻¹.Likewise, for a liquid phase process the weight hourly space velocity(WHSV) of the olefin component may vary over a wide range, but typicallyis greater than about 0.01 g olefin per g catalyst per hour (hr⁻¹),preferably, greater than about 0.05 hr⁻¹, and more preferably, greaterthan about 0.1 hr⁻¹. Typically, the WHSV of the olefin is less thanabout 100 hr⁻¹, preferably, less than about 50 hr⁻¹, and morepreferably, less than about 20 hr⁻¹. The gas and weight hourly spacevelocities of the oxygen, hydrogen, and diluent components can bedetermined from the space velocity of the olefin taking into account therelative molar ratios desired.

When an olefin having at least three carbon atoms is contacted withoxygen in the presence of hydrogen and the catalyst describedherein-above, the corresponding olefin oxide (epoxide) is produced ingood productivity. The most preferred olefin oxide produced is propyleneoxide.

The conversion of olefin in the process of this invention can varydepending upon the specific process conditions employed, including thespecific olefin, temperature, pressure, mole ratios, and form of thecatalyst. As used herein, the term “conversion” is defined as the molepercentage of olefin which reacts to form products. Generally, theconversion increases with increasing temperature and pressure anddecreases with increasing gas hourly space velocity. Typically, anolefin conversion of greater than about 0.05 mole percent is achieved.Preferably, the olefin conversion is greater than about 0.2 percent.

Likewise, the selectivity to olefin oxide can vary depending upon thespecific process conditions employed. As used herein, the term“selectivity” is defined as the mole percentage of reacted olefin whichforms a particular product, desirably the olefin oxide. Generally, theselectivity to olefin oxide will decrease with increasing temperatureand increase with increasing space velocity. The process of thisinvention produces olefin oxides in unexpectedly high selectivity. Atypical selectivity to olefin oxide in this process is greater thanabout 50, preferably, greater than about 70, and more preferably,greater than about 90 mole percent. A selectivity to propylene oxide ofgreater than about 99 mole percent at 50° C. has been achieved. Even at165° C. the selectivity to propylene oxide is surprisingly high, betweenabout 85 and 95 mole percent.

Advantageously, the hydrogen efficiency in the process of this inventionis satisfactory. Some additional hydrogen may be burned directly to formwater. Accordingly, it is desirable to achieve a water/olefin oxidemolar ratio as low as possible. In the process of this invention, thewater/olefin oxide molar ratio is typically greater than about 2/1, butless than about 15/1, and preferably, less than about 10/1, and morepreferably, less than about 7/1.

The catalyst of this invention exhibits evidence of a long lifetime. Theterm “lifetime” as used herein refers to the time measured from thestart of the oxidation process to the point at which the catalyst afterregeneration has lost sufficient activity so as to render the catalystuseless, particularly commercially useless. As evidence of its longlifetime, the catalyst remains active for long periods of time withlittle deactivation. Typically, a run time greater than about 100 hourswithout catalyst deactivation has been achieved in a fixed bed reactor.In a preferred mode, a run time greater than about 550 hours withoutcatalyst deactivation has been achieved. The preferred run time betweenregenerations will depend upon the reactor design and may range fromminutes for transport bed reactors to several months for fixed bedreactors. As further evidence of its longevity, the catalyst of thisinvention can be regenerated through multiple cycles without substantialloss in catalyst activity or selectivity.

When its activity has decreased to an unacceptably low level, thecatalyst of this invention can be easily regenerated. Any catalystregeneration method generally known to those skilled in the art can beused with the catalyst of this invention provided that the catalyst isreactivated for the oxidation process described herein. One suitableregeneration method comprises heating the deactivated catalyst at atemperature between about 150° C. and about 500° C. under an atmosphereof a regeneration gas containing hydrogen and/or oxygen and optionallyan inert gas. A preferred regeneration temperature varies between about200° C. and about 400° C. The amounts of hydrogen and/or oxygen in theregeneration gas can be any which effectively regenerates the catalyst.Preferably, the hydrogen and/or oxygen comprises from about 2 to about100 mole percent of the regeneration gas. Suitable inert gases arenon-reactive and include, for example, nitrogen, helium, and argon. Theregeneration cycle time, that is the time during which the catalyst isbeing regenerated, can range from as little as about 2 minutes to aslong as several hours, for example, about 20 hours at the lowerregeneration temperatures. In an alternative embodiment, water isbeneficially added to the regeneration gas in an amount preferablyranging from about 0.01 to about 100 mole percent.

The invention will be further clarified by a consideration of thefollowing examples, which are intended to be purely exemplary of the useof the invention. Other embodiments of the invention will be apparent tothose skilled in the art from a consideration of this specification orpractice of the invention as disclosed herein. Unless otherwise noted,all percentages arc given on a weight percent basis.

Preparation of Titanium Silicalite TS-1 having Si/Ti=100

Tetraethylorthosilicate (Fisher TEOS, 832.5 g) was weighed into a 4liter stainless steel beaker and sparged with nitrogen gas for 30minutes. Titanium n-butoxide (DuPont, Ti(O-n-Bu)₄) was injected from asyringe into the silicate. The weight of the titanium n-butoxide whichwas added to the TEOS was 14.07 g, taken by difference. A clear yellowsolution was formed. The solution was heated and stirred under nitrogenfor about 3 hr. The temperature varied from 50° C. to 130° C. Thesolution was then chilled in an ice bath.

A 40 percent aqueous solution of tetrapropylammonium hydroxide (TPAOH,710.75 g) was weighed into a polyethylene bottle, which was capped andplaced in an ice bath. The TPAOH was added dropwise to the chilled TEOSsolution with vigorous stirring by an overhead stirrer. After one-halfof the TPAOH had been added, the TEOS solution was cloudy and began tothicken. Within five minutes the solution froze completely. At thispoint the remainder of the TPAOH was added, the gel was broken up with aspatula, and stirring was resumed. Deionized water (354 g) was added,and the solution was warmed to room temperature. After 5 hr the solidshad largely dissolved, and an additional quantity of deionized water(708 g) was added. Stirring was continued overnight yielding a clearyellow synthesis gel containing no solids.

The synthesis gel was poured into a 1 gallon (3.785 liters) stainlesssteel autoclave and sealed. The autoclave was heated to 120° C. and thengradually to 160° C. where it was kept for 6 days. The reactor contentswere stirred at all times. At the end of the reaction period, theautoclave was cooled and a milky white suspension was recovered. Thesolids were recovered, washed, centrifuged, and resuspended in deionizedwater. The solids were filtered, dried at room temperature, heatedslowly to 550° C., and calcined thereat for 8 hr. The solid wasidentified as having an MFI structure, as determined by XRD. Ramanspectra did not reveal any known crystalline titania phase. A Si/Tiatomic ratio of 100 was found, as measured by X-ray fluorescence (XRF).Yield of titanium silicalite-1: 106 g.

EXAMPLE 1

Preparation of Epoxidation Catalyst

Titanium silicalite TS-1 (10.042 g) having a Si/Ti atomic ratio of 100,prepared as described hereinabove, was added to an aqueous solution ofchloroauric acid, HAuCl₄.3H₂O (0.4829 g in 50 ml water). The pH wasadjusted to between 7 and 8 by adding sodium carbonate. Magnesiumnitrate, Mg(NO₃)₂.6H₂O (1.97 g), was added as was more sodium carbonateuntil the pH was between 7 and 8. The total amount of sodium carbonateused was 0.62 g. The mixture was stirred overnight. A solid product wasfiltered, and the filtercake was washed 3 times with 150 ml of water.The wet filtercake was dried at 100° C. for 2 hr. The dried solid washeated over an 8 hr period to 400° C. and then calcined under air at400° C. for 5 hr to yield an epoxidation catalyst comprising gold onTS-1. Catalyst composition as determined by neutron activation analysis(NAA) was the following: Au, 1.07, Si 41.0, Ti 0.77, Mg 0.21, and Na0.31 percent. The average gold particle size was 35 Å, as determined byTEM.

EXAMPLE 2

Oxidation of Propylene to Propylene Oxide

The epoxidation catalyst of Example 1 was tested in the direct oxidationof propylene to propylene oxide. The catalyst (5 cc) was loaded into a10 cc fixed-bed, continuous flow reactor with flows of helium, oxygen,hydrogen, and propylene. Total flow rate was 150 cc/min (or GHSV 1,800hr⁻¹). Feedstream composition was 5.0 mole percent hydrogen, 10.5 molepercent oxygen, and 53.6 mole percent propylene, the balance beinghelium. Propylene, oxygen and helium were used as pure streams; hydrogenwas mixed with helium in a 20 H₂/80 He (v/v) mixture. Pressure wasatmospheric; reactor temperature ranged from 50° C. to 165° C. Productswere analyzed using an on-line gas chromatograph (Chrompack™ Poraplot™ Scolumn, 25 m) with the results shown in Table 1.

TABLE 1 Direct Oxidation of Propylene (PP) to Propylene Oxide (PO) UsingGold on TS-1 (Si/Ti = 100)^(a) Time T Conv PP Sel PO (hr) (° C.) (mol %)(mol %) H₂O/PO 0.5 50 0.008 57.1 — 1 50 0.019 84.8 — 3 50 0.064 96.8 — 750 0.123 98.3 5.59 11 50 0.164 99.3 2.85 14 50 0.160 99.0 2.88 19.5 600.211 98.8 3.40 22 70 0.287 98.3 4.06 24 80 0.366 97.6 4.67 40 80 0.20097.5 5.26 60 90 0.180 96.1 7.74 73 110 0.264 91.8 12.20 119^(b) 1100.128 95.0 8.32 140 120 0.108 93.5 8.85 176^(c) 150 0.289 88.2 20.50 208165 0.423 84.6 18.00 258 165 0.444 86.0 13.17 275 165 0.446 85.5 15.27^(a)Feedstream (mol %): 5.0% H₂, 10.5% O₂, 53.6% propylene, balancehelium; flow 150 cc/min; pressure atmospheric ^(b)Flow increased at 119hr to 300 cc/min. ^(c)Flow increased at 176 hr to 400 cc/min.

It is seen that a composition comprising gold with magnesium on TS-1having a Si/Ti molar ratio of 100 is capable of catalyzing the directoxidation of propylene to propylene oxide. Activity increases withincreasing temperature with a propylene conversion of 0.20 mole percentat 110° C. Selectivity to propylene oxide reaches a maximum of over 99mole percent. The water/propylene oxide molar ratio is good, and thecatalyst remains active at 275 hr.

Preparation of Titanium Silicalite TS-1 having Si/Ti=27

Tetraethylorthosilicate (Fisher TEOS, 1250 g) was weighed into a 3 literErlenmeyer flask and sparged with nitrogen gas for 30 minutes. Titaniumn-butoxide (DuPont, Ti(O-n-Bu)₄, 51.2 g) was injected from a syringeinto the TEOS with vigorous stirring. The flask was placed in a 50° C.water bath, stirred for 1 hr, and left to stand for about 60 hr with anitrogen pad.

A 40 percent solution of tetrapropylammonium hydroxide (Sachem TPAOH,1069.7 g) was added to deionized water (540 g) in a 2 liter beaker andchilled in an ice bath. The TEOS was also chilled in an ice bath. Whenboth solutions were chilled below 10° C., the TEOS solution wastransferred to a 4 liter stainless steel beaker equipped with anoverhead stirrer. The TPAOH solution was added dropwise by means of anaddition funnel. Addition was completed over 5 hr to form a clear yellowsynthesis gel.

The synthesis gel was poured into a 1 gallon (3.785 liters) stainlesssteel autoclave and sealed. The autoclave was heated to 100° C. forabout 2 hr and then to 140° C. for about 2 hr and then to 160° C. for 6days. The reactor contents were stirred at all times. At the end of thereaction period the autoclave was cooled and a milky white suspensionwas recovered. The solids were recovered, washed, centrifuged, andresuspended in deionized water. The washing was repeated three timesuntil the pH of the wash water was below pH 9. The solids were dried at65° C. overnight to form white cakes, which were crushed to pass a 20mesh sieve. This solid was heated to 500° C. over 8 hr and then calcinedunder air at 500° C. for 2 hr. The solid was identified by XRD to havean MFI structure. Raman spectra revealed titania in the anatase phase(about 50 percent of the total weight of titanium). The Si/Ti atomicratio was determined to be 27 by XRF. Yield: 175.5 g.

EXAMPLE 3

Preparation of Epoxidation Catalyst

A catalyst composition comprising gold on TS-1 having a Si/Ti atomicratio of 27 was prepared according to the method of Example 1, with theexception that the following amounts of reagents were used: TS-1, 10.07g; chloroauric acid, 0.4876 g in 50 ml water; sodium carbonate 0.60 gtotal; and magnesium nitrate, 1.98 g. Catalyst composition as determinedby NAA was the following: Au 0.71, Si 41.9, Ti 2.39, Mg 0.18, and Na0.24 percent. The average gold particle size was 18 Å, as measured byTEM.

EXAMPLE 4

Oxidation of Propylene to Propylene Oxide

The epoxidation catalyst of Example 3 was tested in the direct oxidationof propylene to propylene oxide in a manner similar to that described inExample 2 with the results shown in Table 2.

TABLE 2 Direct Oxidation of Propylene (PP) to Propylene Oxide (PO) UsingAu/TS-1 (Si/Ti = 27)^(a) Time T Conv PP Sel PO (hr) (° C.) (mol %) (mol%) H₂O/PO 0.5 35 0.007 52.9 — 1.0 50 0.019 93.8 — 1.5 60 0.168 99.0 5.434 60 0.173 99.3 3.17 6 60 0.149 99.5 2.52 8 60 0.132 99.4 2.85 94 600.042 100 3.49 96 70 0.067 99.4 3.55 101 80 0.109 99.3 3.29 117 80 0.08899.1 3.46 122 90 0.131 99.1 3.62 150 110 0.175 98 5.39 240 110 0.120 977.01 250 140 0.25 97 9.19 275^(b) 150 0.25 97 10.48 300^(c) 165 0.34 959.33 ^(a)Feedstream (mol %): 5.0% H₂, 10.5% O₂, 53.6% propylene, balancehelium; pressure atmospheric; flow 150 cc/min ^(b)Flow increased at 275hr to 300 cc/min. ^(c)Flow increased at 300 hr to 500 cc/min.

It is seen that a composition comprising gold and magnesium on TS-1having a Si/Ti molar ratio of 27 is capable of catalyzing the directoxidation of propylene to propylene oxide. Propylene conversionincreases with increasing temperature to a value of 0.25 mole percent at140° C. Selectivity to propylene oxide remains over 90 mole percent andreaches a maximum of nearly 100 percent. The water/ propylene oxidemolar ratio is good, and the catalyst remains active at 300 hr.

EXAMPLES 5(a) and 5(b)

Preparation of Catalysts and Evaluation in the Oxidation of Propylene toPropylene Oxide

Two catalysts were prepared as follows. Chloroauric acid was dissolvedin water (50 g). TS-1 having a Si/Ti of 27, prepared hereinabove, wasadded to the solution with stirring. In sample 5(a) sodium was added asa promoter. In sample 5(b) erbium and sodium were added as promoters.The mixtures were stirred for 1 hr. Sodium carbonate was added to eachmixture to adjust the pH to between 7.0 and 7.6. The solution wasstirred for 1.0 hr, and the pH was readjusted if needed with sodiumcarbonate. The mixture was stirred overnight. A solid was filtered fromeach sample and washed three times with water (150 cc per wash). Thesolid was dried at 110° C. for 1 hr in air, crushed lightly to break bigparticles, then calcined in air at 120° C. for 3 hr. Then, the solid washeated to 400° C. over 8 hr and held at 400° C. for 5 hr. Afterwards,the solid was cooled to 350° C. for 1 hr and then to room temperature toyield a catalyst comprising gold supported on TS-1. The amounts ofreagents used are listed for each catalyst.

Ex. 5(a): chloroauric acid, 0.217 g; TS-1, 10.040 g; sodium carbonate,0.218 g;

Ex. 5(b): chloroauric acid, 0.134 g; TS-1, 5.054 g; erbium nitrate,1.048 g; sodium carbonate, 0.596 g.

The average size of the gold particles was 30 Å for catalyst 5(a) and 35Å for catalyst 5(b), as measured by TEM. Gold loading was about 0.7percent for both catalysts; erbium loading was 6.5 percent, asdetermined by XRF.

The catalysts were evaluated in the oxidation of propylene to propyleneoxide in a manner similar to that described in Example 2, with theexception that the feedstream comprised 10 mole percent hydrogen, 10mole percent oxygen, 30 mole percent propylene, and the balance helium.Results are set forth in Table 3.

TABLE 3 Direct Oxidation of Propylene (PP) to Propylene Oxide (PO) OnAu/TS-1 Catalysts^(a) Metal Time Promoter on Other T Stream Conv PP SelPO Ex. Than Na (° C.) (hr) (mol %) (mol %) 5(a) None 70 15 0.09 97.5 ″ ″110 18 0.25 95.6 ″ ″ 140 130 0.40 92.0 5(b) Er (6.5%) 70 15 0.15 98.2 ″″ 110 18 0.44 96.7 ″ ″ 140^(b) 130 0.45 92.0 ^(a)Feedstream (mol %): 10%H₂, 10% O₂, 30% propylene, balance helium; flow 150 cc/min, pressureatmospheric; Catalyst 5(a), 10 cc; Catalyst 5(b), 5 cc. ^(b)Flowincreased at 140° C. to 200 cc/min.

Both catalysts are seen to catalyze the direct oxidation of propylene topropylene oxide. When Example 5(a) is compared with Example 5(b) underidentical process conditions, it is seen that the catalyst with theerbium promoter has a higher conversion at about the same selectivity.In Example 5(b) conversion reaches 0.44 mole percent at a selectivity topropylene oxide of 96.7 mole percent.

EXAMPLE 6

Evaluation of Regenerated Catalysts

The used catalysts of Examples 5(a) and 5(b) were removed from thereactors and put into an air oven at 400° C. and stirred every 30 minfor a total of 2 hr to yield regenerated catalysts which were evaluatedin the oxidation of propylene to propylene oxide as shown in Table 4,Examples 5(a)-1 and 5(b)-1. The catalysts were regenerated a second timeat 220° C. in 10 mole percent oxygen in helium and then cooled to 130°C. where they were evaluated in the oxidation process, as shown in Table4, Examples 5(a)-2 and 5(b)-2. The catalysts were regenerated a thirdtime at 250° C. in 10 mole percent oxygen in helium and then cooled to130° C. where they were evaluated in the oxidation process, as shown inTable 4, Example 5(a)-3 and 5(b)-3. The erbium promoted catalyst washeated to 385° C. overnight in the oxygen/helium mixture and evaluatedin the oxidation process as shown in Table 4, Example 5(b)-4.

TABLE 4 Use of Regenerated Catalysts in Direct Oxidation ofPropylene(PP) to Propylene Oxide (PO)^(a) T Time on Conv PP Sel. PO Ex.(° C.) Stream (hr) (mol %) (mol %) 5(a)-1 110 2 0.18 91 ″ 110 8 0.16 93110 12 0.15 93 ″ 130 24 0.20 92 5(a)-2 130 4 0.20 94 5(a)-3 130 4 0.2490 5(b)-1 110 2 0.58 97 ″ 110 8 0.30 97 ″ 110 12 0.22 97 ″ 130 24 0.2796 5(b)-2 130 4 0.28 95 5(b)-3 130 4 0.26 89 5(b)-4 130 0.5 0.83 90 ″130 3.5 0.53 92 ″ 130 8 0.46 93 ^(a)Feedstream (mol %):10% H₂, 10% O₂,30% propylene, balance helium; flow 150 cc/min, pressure atmospheric.

It is seen in Table 4 that catalysts regenerated up to four timescontinue to exhibit significant activity at high propylene oxideselectivity.

EXAMPLE 7

Catalyst Preparation and Epoxidation Process

A mesoporous titanosilate, similar to Ti-MCM-41, was obtained and wascharacterized as follows. The presence of Ti and Si was determined byXRF. The XRD pattern of the calcined material showed a single intensepeak at about d=40 Å. The surface area of the material was determined byargon adsorption to be 1543 m²/g with a uniform pore-size distributioncentered at about 30 Å.

A mesoporous titanosilate (10 g) was added to water (700 ml) and themixture was heated to 80° C. A solution consisting of water (150 ml) andchloroauric acid (0.225 g) was added to the mixture containing themesoporous titanosilicate. A solution consisting of water (50 ml) andcalcium nitrate (2.0 g) was added to the mixture. The pH was raised to7.5 with ammonium hydroxide, and the mixture was stirred for 2 hr. Thesolids were filtered and washed with copious amounts of water. Thewashed solids were calcined in 8 hr to 350° C., then held at 350° C. in5 mole percent hydrogen in helium for 3 hr to yield a catalystcomprising gold and calcium on a mesoporous titanosilicate. Gold loadingwas 1 percent, and gold average particle size was 30 Å.

The catalyst (5 g) was tested in the direct oxidation of propylene topropylene oxide in a manner similar to that described in Example 2 withthe results shown in Table 5.

TABLE 5 Propylene (PP) Oxidation to Propylene Oxide (PO) Using Au and Caon Mesoporous Titanosilicate^(a) T Flow Run Time Conv PP Sel PO (° C.)(cc/min) (hr) (mol %) (mol %) 110 100 20 0.07 90 120 75 45 0.08 80 130150 68 0.08 80 140 150 86 0.09 78 145 150 168 0.10 79 150 150 203 0.1078 ^(a)Feedstream (mol %): 10% H₂, 10% O₂, 30% propylene, balancehelium, pressure atmospheric.

It is seen that a composition comprising gold and calcium on amesoporous titanosilicate can catalyze the direct oxidation of propyleneto propylene oxide. At 145° C. the conversion is 0.10 mole percent andthe propylene oxide selectivity is 79 mole percent.

Preparation of Ti-Beta

Titanium tetrachloride (4.00 g) was added with stirring to ethanol (10.0ml) under a nitrogen atmosphere. The resulting solution was added tocolloidal silica (Ludox HS-40, 40 percent SiO₂, 53.12 g) and the mixturewas stirred until a clear sol was obtained. Sodium hydroxide (5.34 g)was dissolved in water (204.14 g). Sodium aluminate (3.23 g, MCB-Merck,47 percent Al₂O₃, 28 percent Na₂O, 25 percent H₂O) was added to thehydroxide solution and stirred until dissolved. Tetraethylammoniumhydroxide solution (40 percent) was added to the sodium hydroxide-sodiumaluminate solution. The sol containing the titanium and silica sourceswas added to the hydroxide-aluminate solution with vigorous stirring.The resulting mixture was stirred and aged for 8 hr at room temperature,then charged into a stirred reactor (450 ml) and aged therein at 165° C.for 3 days. At the end of the crystallization period, the reactor wasquenched in cold water. The product was filtered, washed with wateruntil the washings were at pH 8, and dried overnight at roomtemperature. The dried material was calcined in air by heating to 500°C. over 5 hr and then holding at 500° C. for 4 hr. The calcined materialwas a highly crystalline form of beta, as determined by XRD. Thepresence of Si and Ti were determined by XRF.

EXAMPLE 8

Catalyst Preparation and Epoxidation Process

A catalyst was prepared comprising gold (1 percent) and calcium onTi-beta. The catalyst was prepared as in Example 7 with the exceptionthat Ti-beta was used in place of the mesoporous titanosilicate. Thecatalyst was tested in the direct oxidation of propylene in a mannersimilar to that described in Example 2 with the results shown in Table6.

TABLE 6 Propylene (PP) Oxidation to Propylene Oxide (PO) Using Au and Caon Ti-Beta^(a) T Run Time Conv PP PO Sel (° C.) (hr) (mol %) (mol %) 13069 0.025 75 150 169 0.025 50 160 203 0.030 50 ^(a)Feedstream (mol): 10%H₂, 10% O₂, 30% propylene, balance helium; flow 150 cc/min; atmosphericpressure.

It is seen that a composition comprising gold and calcium on Ti-beta cancatalyze the direct oxidation of propylene to propylene oxide. Theconversion is 0.025 mole percent at 130° C. with a propylene oxideselectivity of 75 mole percent.

EXAMPLE 9

Catalyst Preparation and Epoxidation Process

Three catalysts (A, B, C) comprising gold on TS-1 (Si/Ti=30) wereprepared in a manner similar to Example 5(b) by using the reagentamounts specified in Table 7.

TABLE 7 Quantities of Reagents for Catalyst Preparations Reagent A (g) B(g) C (g) HAuCl₄.3H₂O 0.1056 0.2089 0.4483 TS-1 (Si/Ti = 30) 10.00 10.0010.01 Mg(NO₃)₂.6H₂O 2.00 2.00 2.00 Na₂CO₃ 0.18 0.38 0.56

Catalysts A, B, and C were evaluated in the direct oxidation ofpropylene as in Example 8 with the results shown in Table 8.

TABLE 8 Oxidation of Propylene (PP) to Propylene Oxide (PO) With Au/TS-1Catalyst Conv PP Sel PO Catalyst (mol %) (mol %) A^(a) 0.09 95.2 B^(a)0.15 92.9 C^(a) 0.19 92.7 C^(b) 0.87 92.0 ^(a)Catalyst, 5 cc; Feedstream(mol %): 10% H₂, 10% O₂, 30% propylene, balance helium; 110° C.,atmospheric pressure, flow 250 cc/min. ^(b)Catalyst (8 cc) calcined at375° C. for 3 hr in air. Feedstream (mol %): 6.5% H₂, 6.5% O₂, 35%propylene, balance helium; 90° C., 185 psia (1276 kPa), flow 943 cc/min.

It is seen in Table 8 that at constant temperature, pressure and flowrate, as the gold loading is increased, the conversion of propylene alsoincreases. It is also seen that as the pressure of the process isincreased, the conversion of propylene is significantly increased.Selectivity remains about constant at greater than 90 mole percent underthe process conditions shown.

EXAMPLES 10 (a-f)

Six catalysts were prepared as follows: Chloroauric acid (1.4526 g) wasdissolved in water (500.0 cc). The total solution was divided into 10portions of 50 cc each. A TS-1 support (Ti/Si=31) was prepared in amanner similar to that shown hereinabove for TS-1 having a Ti/Si of 27,with the exception that 1250.4 g of TEOS, 51.83 g of titaniumtetran-butoxide, 1065.2 g of TPAOH, and 531.1 g deionized water wereused. The TS-1 support obtained was crushed to greater than 60 mesh. TheTS-1, in the amount shown in Table 9, was added to 50.0 cc of the goldsolution, and the resulting suspension was stirred at room temperaturefor about 30 min. A promoter metal salt in the amount shown in Table 9was added to each mixture, and the mixture was stirred for 1 hr.

TABLE 9 Catalyst Preparation Exp. 10 TS-1, g Promoter (g) in addition toNa a 5.04 none b 5.01 Mg(NO₃)₂.6H₂O (0.5050 g) c 5.00 Ca(NO₃)₂.4 H₂O(0.4648 g) d 5.04 Ba(NO₃)₂ (0.5128 g) e 5.03 Er(NO₃)₃.5 H₂O (0.9023 g) f5.03 Lu(NO₃)₃.x H₂O (0.9152 g)

Sodium carbonate was added until the pH was 7.6 and the mixture wasstirred for 1 hr. If necessary, more sodium carbonate was added to raisethe pH to 7.6. The mixture was stirred overnight and then allowed to sitover the weekend at room temperature. The mixture was filtered. Thefiltered material was washed with water, then dried at 120° C. in air,then calcined in air over 8 hr to 400° C., and held at 400° C. for 5 hr.Each of the catalysts (5 cc) was tested in the oxidation of propylenewith a flow of 150 cc/min of 30 percent propylene, 10 percent oxygen, 10percent hydrogen, with the balance helium. forth in Tables 10 and 11.

TABLE 10 PP Conversion/PO Selectivity (mole %)^(a,b) Hr T on Ex. 10a Ex.10b Ex. 10c Ex. 10d (° C.) Stream (Na Only) (Mg) (Ca) (Ba) 100 5.50.030/88.2 0.162/97.1 0.159/96.1 0.048/95.2 110 8.5 0.106/96.00.211/93.1 0.182/96.2 0.080/94.5 140 101.5 0.101/94.7 0.235/88.40.195/89.4 0.144/92.5 145 120.0 0.113/94.8 0.229/88.4 0.232/90.20.182/87.7 150 126.5 0.139/94.6 0.275/87.5 0.270/91.0 0.206/85.6 155130.5 0.162/93.8 0.304/85.5 0.327/88.7 0.252/85.9 ^(a)PP = propylene; PO= propylene oxide ^(b)Feed: 30% propylene, 10% oxygen, 10% hydrogen,balance helium; flow = 150 cc/min; pressure atmospheric PP Conversion/POSelectivity (mole %)^(a,b) T Hr 10e 10f (° C.) on Stream (Er) (Lu) 1005.5 0.078/88.8 0.224/96.6 110 21.5 0.108/97.4 0.187/97.2 120 25.50.135/97.2 0.246/96.7 130 43.5 0.187/96.6 0.326/95.7 140 93.5 0.233/95.60.440/89.9 140^(b) 118.5 0.082/97.2 0.186/88.1 145 124.5 0.120/96.90.282/86.6 150 141.5 0.191/93.8 0.342/86.3 155 143.0 0.211/93.80.439/84.3 ^(a)PP = propylene; PO = propylene oxide ^(b)Feed: 30%propylene, 10% oxygen, 10% hydrogen, balance helium; Up to 140° C., flowrate was 150 cc/min; flow rate was raised at 140° C. to 500 cc/min;pressure atmospheric

TABLE 11 Water/Propylene Oxide Molar Ratio^(a) T Hr on 10a Ex. 10b Ex.10c Ex. 10d (° C.) Stream (Na only) (Mg) (Ca) (Ba) 100 5.5 23.05 7.178.38 12.39 110 8.5 3.93 5.70 7.90 14.92 140 101.5 7.35 7.33 9.86 9.34145 120 7.24 7.63 9.50 11.21 150 126.5 7.40 8.23 10.87 12.44 155 130.56.61 9.09 10.84 12.30 ^(a)Feed: 30% propylene, 10% oxygen, 10% hydrogen,balance helium; flow rate = 150 cc/min; pressure atmosphericWater/Propylene Oxide Molar Ratio^(a) T Hr on Ex 10e Ex 10f (° C.)Stream (Er) (Lu) 100 5.5 8.16 5.97 110 21.5 5.88 5.92 120 25.5 5.87 6.60130 43.5 6.99 8.74 140 93.5 7.54 13.73  140^(b) 118.5 8.82 33.12 145124.5 7.64 13.5 150 141.5 7.35 16.55 155 143 7.81 13.68 ^(a)Feed: 30%propylene, 10% oxygen, 10% hydrogen, balance helium; Up to 140° C., flowrate was 150 cc/min. Flow rate was raised at 140° C. to 500 cc/min;pressure atmospheric

It is seen in Tables 10 and 11 that catalysts containing gold and Group2 or rare earth lanthanide metals supported on TS-1 are active catalystsfor the direct oxidation of propylene to propylene oxide.

EXAMPLES 11 (a-d)

Four catalysts were prepared as follows: Chloroauric acid (1.4539 g) wasdissolved in water (500.0 cc) A 50 cc portion of the gold solution wasused to make each catalyst sample. A TS-1 support (Si/Ti=31; greaterthan 60 mesh) was added in the following amount to the solution: (a)5.03 g; (b) 5.03 g; (c) 5.03 g; and (d) 5.05 g. The resulting suspensionwas stirred at room temperature for about 1 hr. The pH of the solutionwas adjusted to 7.6 with one of the following carbonate salts (a)lithium carbonate; (b) potassium carbonate; (c) rubidium carbonate; and(d) cesium carbonate. The mixture were stirred for 1 hr and then morecarbonate salt was added if necessary to raise the pH to 7.6. Themixture was stirred overnight at room temperature. The mixture wasfiltered, and the filtered material was washed with water (150 cc). Thewet solid was dried at 120° C. in air and then calcined in air over 8 hrto 400° C. and held at 400° C. for 5 hr. Each of the catalysts (5 cc)was tested in the oxidation of propylene with a flow of 150 cc/min of 30percent propylene, 10 percent oxygen, 10 percent hydrogen, with thebalance helium. Results are set forth in Tables 12 and 13.

TABLE 12 PP Conversion/PO Selectivity (mole %)^(a,b) T Hr on Ex. 11a Ex.11b Ex. 11c Ex. 11d Ex. 13 (° C.) Stream (Li) (K) (Rb) (Cs) (NH)^(c) 1004.5 .014/82.8 .048/92.1 .039/90.4 .039/90.4 .060/73.0 110 7.5 .064/95.5.120/96.9 .070/94.6 .099/95.7 .095/78.4 110 24 .042/95.1 .075/97.1.055/95.7 .070/98.1 .075/67.3 120 28 .041/96.7 .092/96.4 .072/95.6.093/96.9 .099/68.7 120 48.5 .026/99.9 .090/96.5 .071/95.3 .091/97.4.074/72.2 130 54 .034/95.8 .122/96.1 .101/95.0 .125/96.2 .122/56.1 13069 .030/95.2 .131/96.0 .111/94.9 .128/96.2 .119/54.0 130 71.5 — — — —.061/68.7 140 73 .039/95.1 .163/95.2 .135/94.2 .179/95.8 .086/65.1 14579 .037/94.9 .194/94.6 .163/93.4 .222/95.3 .131/61.6 145 93.5 .035/94.7.198/94.6 .178/93.8 .226/95.4 .105/56.0 150 99.5 .040/93.1 .225/94.4.203/93.1 .273/94.9 .163/58.8 155 105 .045/92.8 .250/94.1 .230/92.3.320/94.2 160 117.5 .050/92.3 .290/93.6 .270/89.0 .366/93.7 165 122.5.053/93.1 .323/92.8 .297/91.3 .465/92.9 170 143.5 .061/93.0 .364/90.0.331/88.3 .479/91.8 175 149 .074/84.9 .405/88.9 .369/86.7 .539/91.2^(a)PP = propylene; PO = propylene oxide ^(b)Feed: 30% propylene, 10%oxygen, 10% hydrogen, balance helium; flow rate = 150 cc/min; pressureatmospheric ^(c)Flow rate increased in Ex. 13 at 71.5 hr to 500 cc/min.

TABLE 13 Water/Propylene Oxide Molar Ratio^(a) T Time Ex. 11a Ex. 11bEx. 11c Ex. 11d Ex. 13 ° C. hr (Li) (K) (Rb) (Cs) (NH₄)^(b) 100 4.550.38 12.71 8.92 10.72 38.29 110 7.5 8.90 5.49 7.43 5.90 28.78 110 248.62 3.47 7.35 4.45 40.95 120 28 10.28 6.05 5.80 5.42 48.57 120 48.513.21 6.97 8.11 5.98 60.97 130 54 14.52 6.60 7.60 5.32 94.93 130 69 15.27.33 6.64 5.31 98.42 130 71.5 — — — — 40.80 140 73 11.54 6.67 6.64 5.2347.74 145 79 13.64 6.95 6.74 5.58 56.81 145 93.5 12.33 7.40 7.52 6.0964.88 150 99.5 16.59 8.16 6.73 5.68 64.00 155 105 16.80 8.04 7.79 5.84160 117.5 13.81 7.82 8.88 6.67 165 122.5 11.97 9.51 7.79 6.46 170 143.510.08 9.90 9.84 9.45 175 149 11.87 11.43 11.24 10.56 ^(a)Feed: 30%propylene, 10% oxygen, 10% hydrogen, balance helium; flow rate = 150cc/min; pressure atmospheric ^(b)Flow rate increased in Ex. 13 at 71.5hr to 500 cc/min.

It is seen in Tables 12 and 13 that a catalyst comprising gold and aGroup 1 promoter metal supported on a porous titanosilicate is an activecatalyst for oxidizing propylene with oxygen to propylene oxide.

EXAMPLE 12

A catalyst was prepared as in Example 1 using the following amounts ofreagents: chloroauric acid, 0.1225 g in water (50 cc); TS-1 support,10.0157 g; magnesium nitrate, 1.99 g; and sodium carbonate, 0.1318 g.The catalyst (5 cc, 3.25 g) was tested in the oxidation of propylenewith oxygen in the manner described in Example 2 with the results shownin Table 14.

TABLE 14 Oxidation of Propylene to Propylene Oxide^(a,b) Time T Flow %PP % PO hr ° C. cc/min Conv Sel 61 70 150 0.03 95.5 150 80 150 0.0998.31 170 100 150 0.17 98.73 200 110 150 0.17 97.83 250 120 150 0.1697.48 300 125 150 0.16 97.01 350 136 250 0.16 97.45 400 140 250 0.1797.11 550 160 500 0.11 95.83 579 180 500 0.13 96.00 581^(c) 180 500 0.1794.33 ^(a)PP = propylene; PO = propylene oxide ^(b)Feed: 25% propylene,10% oxygen, 10% hydrogen, balance helium; pressure atmospheric^(c)Feedstream also contained 1 mole percent water.

It is seen that the catalyst of Example 12 containing gold and magnesiumon a TS-1 support is active and highly selective to propylene oxide at580 hr on stream. The addition of water to the feedstream has abeneficial effect on raising the conversion.

EXAMPLE 13

A catalyst is prepared as in Example 11 with the exception that 5.05 gof TS-1 are used and ammonium carbonate is employed to adjust the pH.The catalyst is tested in the oxidation of propylene as in Example 11with the results shown in Tables 12 and 13. It is seen that propyleneoxide is produced in a selectivity of over 50 mole percent.

What is claimed is:
 1. A catalyst composition comprising gold on acrystalline titanosilicate, the catalyst being essentially free of aGroup VIII metal and being prepared by a process comprising depositingan anionic gold compound onto a crystalline titanosilicate andthereafter calcining, heating, or reducing the resulting titanosilicateunder conditions sufficient to prepare the catalyst composition.
 2. Thecomposition of claim 1 wherein the crystalline titanosilicate has poresranging in size from 4 Å to about 200 Å in diameter.
 3. The compositionof claim 1 wherein the crystalline titanosilicate is a crystallineporous titanosilicate selected from TS-1, TS-2, Ti-beta, Ti-ZSM-12,Ti-ZSM-48, and Ti-MCM-41.
 4. The composition of claim 1 wherein the goldis present as particles having an average size of 10 Å or greater. 5.The composition of claim 4 wherein the gold is present as particleshaving an average size of greater than 10 Å and less than 500 Å.
 6. Thecomposition of claim 1 wherein the gold is present in an amount greaterthan 0.01 and less than 20 weight percent.
 7. The composition of claim 1wherein the catalyst is essentially free of the anatase phase oftitanium dioxide.
 8. The composition of claim 1 wherein the catalyst issubstantially free of titanium dioxide.
 9. The composition of claim 1wherein the composition is bound to or supported on a support.
 10. Thecomposition of claim 9 wherein the support is selected from silicas,aluminas, aluminosilicates, magnesia, titania, carbon, and mixturesthereof.
 11. The composition of claim 1, being prepared by a processcomprising contacting the titanosilicate with a solution containing agold compound, wherein the gold compound is selected from the groupconsisting of chloroauric acid, sodium chloroaurate, potassiumchloroaurate, gold cyanide, potassium gold cyanide, and diethylamineauric acid trichloride, wherein the pH of the solution is between 5 and11 and the pH is adjusted with a base selected from the group consistingof sodium hydroxide, sodium carbonate, potassium carbonate, cesiumhydroxide, and cesium carbonate, the contacting being conducted at atemperature between 20° C. and 80° C.; and thereafter recovering solidsand calcining the solids under air or under a reducing atmosphere orheating the solids in an inert atmosphere at a temperature between 250°C. and 800° C.
 12. The composition of claim 11 wherein the gold compoundis chloroauric acid.
 13. The composition of claim 11 wherein thereducing atmosphere is hydrogen.
 14. A catalyst composition comprisinggold on a crystalline titanosilicate, the catalyst being essentiallyfree of a Group VIII metal and being prepared by a process comprisingcontacting the crystalline titanosilicate with a solution containing ananionic gold compound at a temperature and pH sufficient to precipitatethe gold compound onto the titanosilicate; thereafter recovering solids,and calcining the recovered solids under air or under a reducingatmosphere, or heating the recovered solids in an inert atmosphere underconditions sufficient to prepare the catalyst composition.